1. Field of the Invention
The present invention relates to a method for managing the connection of digital devices connected to a digital interface through the digital interface, and more particularly, to a method for managing a digital interface in which, when a connection is established between digital devices connected through a digital interface such as The Institute of Electrical and Electronics Engineers, Inc., (IEEE) 1394, access by a third-party device can be controlled through the connection.
2. Description of the Related Art
A plurality of digital devices can be interconnected through a digital interface which conforms to an interface standard such as the IEEE 1394 standard, and a method for managing the connections between those digital devices is prescribed in the International Electrotechnical Commission (IEC) 61883 standard. According to the IEC 61883 standard, input and output plugs are defined for each digital device as the entry of an incoming bit stream and the exit of an outgoing bit stream, respectively. Further, the input and output plugs are controlled by managing registers, such as an output master plug register (oMPR), an output plug control register (oPCR), an input master plug register (iMPR), and an input plug control register (iPCR), so that the connection between the digital devices can be managed.
There are two types of connections made between such digital devices: point-to-point connection and broadcast connection. A point-to-point connection is a connection consisting of output and input plugs and a channel therebetween. The connection can be established and overlaid by an arbitrary device, and the device by which the connection is established manages this connection. The broadcast connection is divided into broadcast-in and broadcast-out connections. The broadcast-in is a connection between an input plug and a channel while the broadcast-out is a connection between an output plug and a channel. The broadcast connection can only be established by a device that actually inputs and outputs a bit stream by the broadcast connection, and can only be released by an arbitrary device in the network. All management of the connection, including establishment or release of the point-to-point connection and the broadcast connection, is performed by managing registers such as oMPR, oPCR, iMPR, and iPCR.
FIG. 1 is a diagram for explaining a conventional method for managing connections. FIG. 2 shows the connection related fields oPCR and iPCR that are used in the IEC61883 standard. Referring to FIGS. 1 and 2, a DVCR 10, a first DTV 12, and a second DTV 14 are connected via a IEEE interface. Further, it is assumed that DVCR 10, which is a source device, and first DTV 12, which is a sink device, are connected through a number 33 isochronous channel.
If this connection is a point-to-point connection, the content of the oPCR of DVCR 10 is oPCR.P-2-P_Connection_Counter(P-2-Pcnt)=1, oPCR. Channel_Number (nCh)=33. The content of the iPCR of first DTV 12 is iPCR.P-2-P_Connection_Counter(P-2-Pcnt)=1, iPCR.Channel_Number(nCh)=33. Further, if the operation of the iPCR and oPCR is performed successfully, a point-to-point connection of DVCR 10 and first DTV 12 is considered to be established. The IEEE 1394 modules of DVCR 10 and first DTV 12 are controlled by connection establishment information denoting the connection establishment state of the point-to-point connection, thereby allowing first DTV 12 to receive and see the output content of DVCR 10.
When a connection is established between DVCR 10 and first DTV 12 as described above, if second DTV 14, which is a sink device, is to monitor the output content of DVCR 10, second DTV 14 attempts to establish a point-to-point connection or broadcast-in connection with DVCR 10 by overlaying the connection on the already established point-to-point connection between DVCR 10 and first DTV 12.
In the case where a point-to-point connection is overlaid and established between second DTV 14 and DVCR 10, the content of the oPCR of DVCR 10 is oPCRP-2-P_Connection_Counter(P-2-Pcnt)=2, oPCR.Channel_Number (nCh)=33. The content of the iPCR of second DTV 12 is iPCR.P-2-P_Connection_Counter(P-2-Pcnt)=1, iPCR. Channel_Number (nCh)=33. According to such information, second DTV 14 controls its own IEEE 1394 module, which allows it to receive and see the output content of DVCR 10.
Further, in the case where a broadcast-in connection is overlaid and established between second DTV 14 and DVCR 10, the content of oPCR of DVCR 10 is oPCR.P-2-P_Connection_Counter(P-2-Pcnt)=1, oPCR.Broadcast_Connection_Counter (Boutcnt)=1, oPCR.ChannelNumber (nCh)=33. The content of the iPCR of second DTV 14 is iPCR.Broadcast_Connection_Counter (Bincnt)=1, iPCR. Channel_Number (nCh)=33. In the same manner, second DTV 14 controls its own IEEE 1394 module according to such information, thereby allowing it to monitor the output content of DVCR 10.
Further, if a broadcast connection is made between DVCR 10 and first DTV 12, the content of the oPCR of DVCR 10 is oPCR.Broadcast_connection_Counter(Bincnt)=1, oPCR. Channel_Number (nCh)=33. The content of the iPCR of first DTV 12 is iPCR.Broadcast_Connection_Counter (Bincnt)=1, iPCR. Channel_Number(nCh)=33. In such a manner, if the operation of the iPCR and oPCR is performed successfully, it is considered that a broadcast-out connection is established in DVCR 10 through channel number 33 while a broadcast-in connection is established in first DTV 12 through channel number 33.
The IEEE 1394 modules of DVCR 10 and first DTV 12 are controlled by connection establishment information denoting the state of the establishment of the broadcast connection. Thus, DVCR 10 outputs a bit stream to channel number 33 and first DTV 12 receives the output of channel number 33, thereby allowing first DTV 12 to see the output of DVCR 10. If second DTV 14, which is a sink device, is to see the current output content of DVCR 10 when a connection is established between DVCR 10 and first DTV 12 in such a manner, second DTV 14 attempts to overlay a point-to-point connection on the already established point-to-point connection or to establish a broadcast-in connection with DVCR 10. In the case where a point-to-point connection is overlaid and established between second DTV 14 and DVCR 10, the content of the oPCR of DVCR 10 is oPCR.P-2-P_Connection_Counter(P-2-Pcnt)=1, oPCR.Broadcast_Connection_Counter (Boutcnt)=1, oPCR.Channel_Number (nCh)=33. The content of the iPCR of second DTV 12 is iPCR.Broadcast_Connection_Counter (Bincnt)=1, iPCR. Channel_Number (nCh)=33. Second DTV 14 controls its own IEEE 1394 module according to such information, thereby allowing it to receive and see the output content of DVCR 10. In the case where a broadcast-in connection is established between second DTV 14 and DVCR 10, the content of the oPCR of DVCR 10 is oPCR.P-2-P_Connection_Counter(P-2-Pcnt)=1, oPCR.Broadcast_Connection_Counter(Boutcnt)=1, oPCR.Channel_Number (nCh)=33. The content of the iPCR of second DTV 14 is iPCR.Broadcast_Connection_Counter(Bincnt)=1, iPCR.Channel_Number(nCh)=33. Also, second DTV 14 controls its own IEEE 1394 module according to such information, thereby allowing it to receive and monitor the output content of DVCR 10.
According to the conventional method for managing the connections to a digital interface, when a bit stream is transmitted through an existing point-to-point or broadcast connection between source and sink devices, another device may access the content flowing through the existing connection without the authority of the user, so that free access by other device is allowed. For example, assuming that DVCR 10 and first DTV 12 are both in the parents' room and second DTV 14 is a DTV in the children's room, the content of a bit stream of the VCR watched by the parents can be accessed without any restriction. In other words, the conventional method for managing a digital interface connection has a problem in that a third-party device can arbitrarily access the existing connection, so that privacy cannot be protected when digital devices are connected.